664

664 = 2 x 2 x 2 x 83.

664 is a value of n such that n(n + 7) is a palindrome (445544).

664 is 554 in base 11 and 474 in base 2.

664 is a generalized heptagonal number (A085787).

664 is the solution to the postage stamp problem for 6 denominations and 7 stamps (A001211).

664 is the sum of three distinct positive cubes (A024975): 664 = 8³ + 5³ + 3³.

Source: What's Special About This Number?